Block and panel caving is an efficient technique that uses gravity to extract ore from an ore body. Caverns of broken rock are blasted at an upper level (the undercut level) beneath the ore body to be recovered, extraction tunnels are formed at a lower level (the extraction level) beneath the undercut level and a series of relatively narrow drawbells are blasted between the extraction and undercut levels to allow broken cavern rock to fall through the drawbells into the underlying extraction tunnels through which the rock can be removed. The speed of rock falling through the drawbells is controlled by the speed at which rock is removed through the extraction tunnels and as broken rock falls through the drawbells the caverns gradually collapse further to create more broken rock to feed the drawbells under the influence of gravity.
The terms “block caving” and “panel caving” may be used according to the dimensions of the ore body being mined. Specifically the term “panel caving” may be used in relation to the mining of relatively wide and shallow ore bodies. The term “block caving” may be extended to ore bodies which are relatively deep and may be used as a wide or generic term applying to caving beneath any ore bodies and so include within its scope panel caving. The term “block caving” will be used in this broad sense throughout the remainder of this specification, including the claims, and is to be construed as including panel caving within its scope.
In traditional block cave mining excavation at both the undercut and extraction levels is carried out by drilling and blasting and removing the blasted rock to form undercut tunnels at the undercut level and extraction tunnels at the extraction level. This is a slow process and large block cave mines require significant time to develop and a very significant early investment. Both of these factors make their financial success in terms of net present value extremely sensitive to the speed at which they can be brought on stream. The present invention is concerned with methods to enable quicker development of a block cave mine.